A map data updating technique is known (for example, Patent Literature 1). According to this technique, when a vehicle travels on a road not stored in existing map data, such as a road newly opened to traffic, the map data is automatically changed or corrected or data is automatically added, so that the map data is updated with this road.
Patent Literature 1 describes that an own vehicle location is detected by an own vehicle location detection portion (including various sensors, such as a GPS receiver, a gyro sensor, and vehicle speed sensor) and a travelled track of the own vehicle is created by linking the own vehicle locations as a travelled track of an unregistered road (hereinafter, referred to as the potential unregistered road track). The potential unregistered road track is corrected by taking errors of the respective sensors into account and the corrected potential unregistered road track is stored as new map data corresponding to an unregistered road.
The potential unregistered road track is corrected in Patent Literature 1. In practice, however, the potential unregistered road track may possibly fail to conform to a shape of an actual unregistered road (accuracy is low) due to various errors, in particular, when the vehicle travels a long distance on an unregistered road. By registering the potential unregistered road track with such low accuracy as new map data corresponding to an unregistered road, map data with a significant error is registered. Hence, next time the vehicle travels on this road, the road may possibly be detected again as an unregistered road.